There are many electrical devices today, such as hearing aids, watches, and the like, that utilize button batteries. A typical button battery is shown in U.S. Pat. No. 3,922,178 (the disclosure of which is hereby incorporated herein by reference. Conventional button batteries usually are zinc-silver oxide, or zinc-mercuric oxide cells. Such button batteries are conventionally considered unrechargeable since there are safety concerns associated with trying to recharge such batteries. If too much electricl energy is supplied to such batteries (too much current or voltage) in an attempt to recharge the same, there is a great danger of explosion. For this reason, such batteries are normally discarded after one use.
It has been found according to the present invention that conventional button batteries can be safely and effectively energized so that they may be effectively used for three or more cycles. Reenergization of such batteries is accomplished according to the invention by limiting the amount of electrical energy supplied thereto in a simple and convenient manner.
According to one aspect of the present invention a battery energizer is provided which comprises: conventional solar cell means for generating a small amount of current when light impacts thereon; and terminal means for releasably receiving a button battery therein, and electrically interconnected to the solar cell means. The solar cell means has a controlled maximum current and voltage output (e.g., 20 milliamperes, 3 volts), and preferably a diode is provided electrically interconnected to the solar cell means and the terminal means. The diode allows passage of current only from the solar cell means to the button battery received by the terminal means, but not vice versa. The diode may comprise a light emitting diode (LED) which provides an indication of when the battery has been fully energized, or is being energized; and the LED may be provided in place of, or connected parallel to, a conventional diode (and thus either in series with, or in parallel with, respectively, the terminal means).
The solar cell means, LED, and terminal means preferably are mounted on a mounting plate. The solar cell means are mounted on one side of the mounting plate, and the LED and terminal means on the opposite side. Means are provided defining an opening in the mounting plate for receipt of a hook, which hook is connected up to a suction cup which may be placed against a window or adjacent an artificial light source to support the solar cell means in an appropriate position to receive light thereon.
Preferably the solar cell means are constructed so that the maximum current output therefrom is about 20 milliamperes, and if it is desirable to limit the amount of light incident on the solar cell, a filter may be provided over the solar cell for that purpose.
According to another aspect of the present invention, solar cell means and terminal means are provided for receipt of a plurality of conventional dry cell rechargeable batteries (such as nickel-cadmium batteries), for charging one or more of the rechargeable batteries at the same time in a simple and effective manner. According to this aspect of the invention, the solar cell means and the terminal means are physically and electrically connected, with an LED indicating the status of the charging batteries, and allowing passage of current from the solar cell means to batteries received by the terminal means, but not vice versa. The charger in this embodiment preferably consists of the solar cell means, LED and terminal means, with a zener diode connected in parallel with the terminal means, and between the terminal means and the LED and solar cell means.
According to the second aspect of the present invention, an adaptor is preferably provided to allow a single size of terminal means (e.g., adapted to receive conventional D-size batteries), to receive a wide variety of other, smaller sized batteries too (e.g., to receive AA-size batteries). Further, in case only one battery--or a number of batteries less than the total number of terminal means--is to be charged at a time, particular dummy batteries may be provided to allow charging.